<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>变量-布尔类型</title>
</head>
<body>
    
</body>
<script>
    var str="hello world";
    //非空字符进行布尔判断时会被理解为布尔值true
    if(str){
          alert("值为真");
    }
</script>
</html>